The primary objective of this study is to develop and apply cytochemical and biophysical probes of nuclear and cytoplasmic structure in order to distinguish between normal proliferating, normal differentiating, premalignant and malignant cells. These probes could be used for flow cytometry and cell sorting instruments and could have possible application in screening, diagnosis and classification of premalignant and malignant lesions. Using a variety of nucleic acid-interacting (mostly intercalating) fluorochromes the following cell parameters will be studied: 1) Simultaneous measurement of total cellular RNA and DNA, and RNA/DNA ratios; 2) RNA and DNA content of isolated nuclei (nuclear RNA/DNA ratio); 3) Ratio of double stranded (ds) RNA to single stranded (ss) RNA, or ds RNA/DNA; 4) Chromatin structure as evaluated by DNA sensitivity in situ to thermal- and acid-induced denaturation; 5) Accessibility of DNA in situ to intercalating probes of different sizes and affinities (acridines, quinacrine, actinomycin D, di-acridines); 6) Accessibility of DNA to nucleases; 7) Chromatin structure as studied by combinations of dyes and energy transfer phenomena; 8) Structure of DNA in situ as reflected by a decrease in fluorescence polarization of DNA-bound fluorescent probes; 9) Extent of free-SH groups in chromtin, reacting with SH-specific fluorescent probes; 10) Sensitivity of chromatin to steroid hormone. In addition, instrument development is planned to achieve increased resolution of flow cytometric measurements, and to use dual laser excitation. A number of tissue culture tumor cell lines will be studied as well as normal and mitogen stimulated human lymphocytes and cell suspensions of human uterine cervical, endometrial, colonic and upper respiratory tract carcinomas.